Borrowings - Summary of Bancorps Short Term Borrowings (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
FHLB Advances
Short-term Debt [Line Items]
Maximum outstanding at any month end	$ 2,622,165	$ 2,283,250	$ 1,697,800
Average balance during the year	$ 1,526,180	$ 1,415,755	$ 965,293
Weighted-average interest rate during the year	2.05%	1.44%	0.95%
Federal Funds Purchased
Short-term Debt [Line Items]
Maximum outstanding at any month end	$ 195,000	$ 238,000	$ 137,000
Average balance during the year	$ 156,652	$ 163,466	$ 84,514
Weighted-average interest rate during the year	1.92%	1.19%	0.58%

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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Weighted average interest rate of short-term debt outstanding calculated at point in time.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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For the form of debt having an initial term of less than one year or less than the normal operating cycle, if longer, average borrowings during the period.

+ References

No definition available.

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For the form of debt having an initial term of less than one year or less than the normal operating cycle, if longer, maximum month-end borrowings during the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(19))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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